Archived 4th gear grinds

[tmckenzie]

Last week when shifting under normal driving my transmission would grind goin into 4th. Its been doing it ever since. Synchros Im pretty sure. I can baby it and it wont grind. My question is how long can I baby it without doing more harm? Ive been planning on doing a South Bend clutch this summer for several months and was hoping I could get by with holding off on getting the synchros replaced until I do the clutch. Is this safe or do I need to get to the transmission ASAP?

 

[KBalzuweit]

I had 3rd go in my old truck. It did the same thing. If you had the rpm's right, it would go in. If not GRIND!! I just skipped 3rd as much as possible and put on another 30k and sold it. I just changed my fluid at every oil change to make sure there was no metal in it. I actually got pretty good at getting into 3rd without grinding. It was just to hard to skip when towing.

 

[Extreme1]

I've never seen the inside af a 4500 but if it's like all the other manuals I've done, it won't destroy hard parts. By hard parts I mean things you don't want to replace like gears and shafts. But running small bits of brass through bearings isn't the best for them either. The synchros are probably all brass and the grinding you are hearing is the synchro ring engaging the synchro sleeve. This is a sign of a damaged ring (or sleeve but usually it's the ring) and the grinding sound does remove small bits of brass from the ring and adds it to your lube.



Brass is comparatively soft so no major damage usually occurs but it can increase the wear on all the moving parts if you leave it like that for a while. I'd order the clutch, change the oil and continue to drive it carefully if you don't have anything else to drive. No grind shifts shouldn't be any more contaminating than normal shifts. Also, since the brass is a wear metal, there is a bit present already (but in smaller pieces).



It the synchros are made of a hard material (anything ferrous) I'd park it immediately. For a look at how this all works take a look here , it isn't an actual 4500 but this part of the description is pretty universal.

 

[JTeague]

If 4th is the only gear grinding, its an easy fix by just removing the input shaft. Just take the four bolts out of the front bearing retainer and carefully pull the input shaft out being careful not to lose the roller bearings and thrust bearing on the back of the input shaft where it engages onto the mainshaft. With the inputshaft removed you can easily replace the blocker ring (synchro). It simply pulls out off of the mainshaft. when you install the new blocker ring it has notches that engage into the keys in the inner syncro hub on the mainshaft. Carefully slide the inputshaft back onto the mainshaft. Then reinstall the bearing retainer on the trans. The inputshaft sould turn freely with minimal endplay. This should fix your 4th gear grind. PM me if you would like more detailed instructions.



As for wether or not to keep driving the truck with it grinding, it will more than likely not hurt anything until you get around to fixing it. I drove my 97 for 6 months with 3rd grinding on ever shift. The Gear still looked new and all I did was replace the blocker ring to cure the grinding. When you shift try pausing for a split second before you grab 4th and it probably will fall right in. Hope this helps.